Feline Retroviruses Flashcards
Which feline viruses are classed as retroviruses?
- Feline leukaemia virus (FeLV)
- Feline Immunodeficiency virus (FIV)
- Feline syncytium-forming virus (FeSFV)
Classification of a virus is based on which factors?
- The genome: RNA or DNA
- Number and sense of RNA/DNA strands
- Morphology
- Genome sequence similarity
- Ecology
What is the genome of Retroviridae?
RNA
What are the main characteristics that only this virus classification has?
- Truly diploid
- Genome is produced by cellular transcriptional machinery
- Genome requires a specific cellular RNA for replication
Describe the main structural features of a virus
- Outer glycoproteins for attachment
- Viral envelope
- Inner capsid
- Core of reverse transcriptase and 2 identical RNA strands
What is reverse transcriptase?
Virally encoded RNA dependent DNA polymerase
How does reverse transcriptase work?
Uses the viral RNA genome as a template for the synthesis of complementary DNA copy
The virus need RT as it is not found in the host
What is the role of integrase?
Bind the viral cDNA generated by RT and the host DNA which allows insertion of the viral genome into the hosts DNA, when the host makes copies of its DNA it is also copying the viral DNA
Which subtype of Feline leukaemia virus is transmissible?
type A
How can a host have type B or C FeLV if only type A is transmissible?
B and C are recombinants or mutants of A so are only found with type A and need type A for replication
Name the 4 syndromes caused by FeLV
RAIN
- Reproductive failure
- Anaemia
- Immunodeficiency
- Neoplasia (tumours)
What are the routes of infection for FeLV?
- excreted in saliva, urine, faeces and milk
- requires close FRIENDLY contact
- passed to offspring
Describe the pathogenesis of FeLV
- Replicates in oropharynx and local lymph nodes: primary viraemia: antibody negative, virus positive
- Continues to replicate in lymph and bone marrow: secondary viraemia
- Persistent latent infection: virus negative, antibody positive
- An ineffective immune response leads to clinical disease and death
How does age affect susceptibility to FeLV?
Susceptibility to persistent infection decreases with age
What are the 4 main types of lymphoma associated with neoplasia/FeLV?
- Mediastinal (thymic)
- Multicentric
- Alimentary
- Leukaemic